Hi,    Please ensure if following things are correct1) The array 
bounds are equal. Means \"my_x\" and \"size_y\" has the same value on all 
nodes.2) Nodes are homogenous. To check that, you could decide root to be some 
different node and run the program-NeerajOn Fri, 26 Oct 2007 10:13:15 +0500 
(PKT) Open MPI Users  wrote  Thanks for your reply,     I used MPI_Wtime for my 
application but even then process 0 took longer  time executing the mentioned 
code segment. I might be worng, but what I  see is process 0 takes more time to 
access the array elements than other  processes. Now I dont see what to do 
because the mentioned code segment  is creating a bottleneck for the timing of 
my application.    Can any one suggest somthing in this regard. I will be very 
thankful    regards    Aftab Hussain      On Thu, October 25, 2007 9:38 pm, 
jody wrote:  > HI  > I\'m not sure if that is a problem,  > but in MPI 
applications you shoud use MPI_WTime() for time-measurements  >  > Jody  
>  >  > On 10/25/07, 42af...@niit.edu.pk  wrote:  >  >> Hi 
all,  >> I am a research assistant (RA) at NUST Pakistan in High 
Performance  >> Scientific Computing Lab. I am working on the parallel  
>> implementation of the Finitie Difference Time Domain (FDTD) method 
using  >> MPI. I am using the OpenMPI environment on a cluster of 4  
>> SunFire v890 cluster connected through Myrinet. I am having problem  
>> that when I run my code with let say 4 processes. Process 0 takes 
about 3  >> times more time than other three processes, executing a for 
loop which  >> is the main cause of load imbalance in my code. I am 
writing the code  >> that is causing the problem. The code is run by all 
the processes  >> simultaneously and independently and I have timed it 
independent of  >> segments of code.  >>  >> start = 
gethrtime(); for (m = 1; m < my_x ; m++){ for (n = 1; n > size_y-1; n++) 
{ Ez(m,n) = Ez(m,n) + cezh*((Hy(m,n) - Hy(m-
1,n)) -  >> (Hx(m,n) - Hx(m,n-1)));  >> }  >> }  >> 
stop = gethrtime(); time = (stop-start);  >>  >> In my 
implementation I used 1-D array to realize 2-D arrays.I have used  >>  
the following macros for accesing the array elements.  >>  >> 
#define Hx(I,J) hx[(I)*(size_y) + (J)]  >> #define Hy(I,J) 
hy[(I)*(size_y) + (J)]  >> #define Ez(I,J) ez[(I)*(size_y) + (J)]  
>>  >>  >> Can any one tell me what am I doing wrong here, or 
macros are creating  >> the problems or it can be related to any OS 
issue. I will be looking  >> forward for help because this problem has 
stopped my progress for the  >> last two weeks  >>  >> 
regards aftab hussain  >>  >> RA High Performance Scientific 
Computing Lab  >>  >>  >> NUST Institue of Information 
Technology  >>  >>  >> National University of Sciences and 
Technology Pakistan  >>  >>  >>  >>  >>  >> 
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